I've been testing different products and methods used to keep water from freezing while out in -20 (f) or colder temps for extended periods.

Does anyone know much about the North Face Snowday backpack that has a heated hydration system? Uses AA batteries to provide heat to the tube and mouthpiece (they say 20 hours at 15 degrees) and a sensor to turn the heat on and off as needed. My concern is that the mouthpiece will still freeze up at -20 temps unless I tuck it in my coat, but if I tuck it in my coat the sensor may misread the temp and then allow the tube to freeze… Any info? (TNF has not responded to my email.)

In the meantime I'm going to create a fiberfill insulated tube sleeve and reservoir insulator.

Alec,
I don't have anything to report about tnf heated hydration system, but I have this theory (yet to be tested, I'm afraid) that if you pop a chemical heat pack into the insulating sleeve of your hydration system, it should keep your water from freezing for a while. As for the hose, I'm sure you have devised plenty of methods for preventing that from freezing (from your posts, you seem like you know a lot about operating in deep cold)blowing it back into the bladder, tucking it into the jacket as you mentioned.
I have to admit, all that electrified stuff that tnf is making seemslike its primary market is lift served skiers, it seems to add aditional complexity and weight (batteries, etc.)for limited funcionality
Josh

I don't know about the heated systems you mention but insulating the tube with Aerogel could work as an alternative to fiberfill. It wouldn't compress like the fiberfill insulation would. I haven't tried this but it seems like it would work well. It might take buying 2 sets of the shoe inserts to get enough material if it can't be found otherwise. Just thinking out loud an possibly poorly at that.

I've found that really no amount of insulation will keep the tube from freezing at low temps. The only thing that works for me is making sure to get ALL the water out of the tube and mouthpiece every time you drink. After all, the water in the tube isn't producing any heat, so even if you had a down filled tube cover, you're only delaying the inevitable. I've found with the Camelbak tube cover, you're not delaying it very long.

I totally agree about evacuating the tube and mouth piece. In my mind, the insulation is primarily there for when you are drinking. I just don't know how to quantify its effect. As you are drinking, the water in the tube is cooled and then the remaining water is returned to the main reservoir were it cools your main water supply. As the volume of the reservoir decreases the effect of the blow-back increases. This is a little gross but a little warm backwash might help. It seems to me like any heater or sensor belongs on the reservoir an not on the tube.

I do blow back, but like someone who eats lots of sausages, eventually the artery gets clogged.

Drink, blow back, a tiny drop of water stays in the tube and freezes. It doesn't seal the tube. Drink again, blow back again, this time another slight drop catches where that last drop was. Every drink leaves a slight drop of water, until eventually, she clogs up.

I added insulation to the tube, sewn over the top of my shoulder stap (theory was that heat from my body would travel through the shoulder strap and be held by the tube by the added insulation). The tube was fine under the insulation, froze in the small gap where there was less insulation. Friend from Alaksa showed me her tube (that sounds strange). It had closed cell foam wrapped completely around it. I thought about adding fiberfill instead of foam since I like to tuck the mouthpiece in my coat. Fiberfill will compress, allowing the collar of my coat to actually close… Maybe???

Alec,
Innovative Sports http://www.innovativesports.net …remember that name. These guys can do anything involving the problem you sighted. Innovative Sports introduced a heated jacket as a challege to the MET 5 TNF put out and it drove the MET 5 into extinction. They could make a pencil heater if you want with a thimbal sized battery. Seriously.. I live in Bend, OR and ride at Bachelor every day in my heated jacket from IS for 2 full seasons now. Never given me a moments trouble, and the thing charges from my car, the wall, and even solar. Heats up to 150, with a single battery the size of a deck of cards. They also make a kick ass pitching sleeve that's heated for alot of MLB and college teams. Call those dudes, they probably have something off the shelf they could send you for this. If not its a good excuse to prod them to put something together. They use fabric yarns that heat.

I'm not an experienced winter backpacker but had the same problem with freezing up of my tube. You already know what to do. You say you like to keep it simple. How about taking a 1,5 to 2 liter thermos and make some hot tea???

Yep it's heavy, but no hose to freeze up!
Yep it's a lot more extra work as compared to sucking water trough a hose, but you can schedule a tea break every 15 to 20 minutes and have a cup of hot tea with the benefit of being warmed from the inside out.

I think Alec was planning on stopping every 4 hours or so to boil water etc for the AH135 race. I personally would be opposed to stopping every 20 minutes in a race type situation. Now if I was just winter hiking for pleasure that would be a different story. I like a nice cup of tea :)

Well if I would be racing than there definitely wouldn't be time for tea breaks.

A platypus does however hold warm liquids. I wonder if an insulated bladder will give as good a performance as a thermos will. I also wonder if sucking warm tea trough the tube will help keep it frost free for a longer period or if the increased vapor from a warm liquid will actualy speed up the freezing up process.

Interesting trivia in this perspective is that an ice cube tray filled with warm (hot) water will freeze faster than an icecube tray flled with water straight from the tap.

The suggestion of the ice cube tray would need to be tested (empirically evaluated).

There is supposedly only a very narrow range of experimental conditions where it can be demonstrated that water at a higher starting temp will freeze before water starting at a colder temp. The container itself seems to play a role in these experiements relative to heat transfer and evaporation.

There are a number of reasons for this phenonmenon (supposedly first noticed by Aristole and not to the student to whom this and the name of the effect is often attributed) and the fact that it won't happen under a very many great experimental conditions. In the event of the Platy, evaporation won't occur (since it's a sealed container) which is supposedly a main contributing factor to the rare instance when hot will freeze before cold. Obviously, when evaporation is introduced we are no longer comparing identical test specimens. It is for this reason, i am told by a PhD here, that we often use very hot water when conducting icing tests on aircraft. I suspect that it could be for another reason however.

I tried this experiment as a kid, b/c it sounded strange that Aristotle would say such a thing and was also non-intuitive to me. In my few tests before my mother insisted that i stop opening the freezer, the cold water froze first before the hot water. It was only later that i found out that one could design a very arbitrary experiment that could make hotter water freeze before colder water. Usually, the facts are totally blown out of proportion in more poplular writings when it comes to this subject.

Anyways, we now return to our regularly scheduled BackpackingLight programming…

pj, this has been an ongoing debate in the winter race group. The organizers told us that hot water will freeze first so put cold water in your reservoir. I scoffed a bit at this since the research does seem to show 1) that it is under very limited circumstances that this can occur and 2) as you say, evaporative cooling does not happen in a reservoir. Experience has told me that warm water stays liquid longer in the reservoir.

Aristotle also said that a heavier object will fall faster than a lighter object if both are dropped simultaneously. He apparently never tested this hypothesis (unless the lighter object was a feather???). Galileo, of course, proved otherwise – though he was mocked and considered insane at the time for disagreeing with the likes of Aristotle.